1. Field of the Invention
The present invention relates to a disk control system comprising a small computer system interface (SCSI) control circuit as communicating means between a magnetic disk, an optical disk or the like and a host system, thereby transferring and receiving data to and from a magnetic disk system, an optical disk system and the like.
2. Description of the Prior Art
FIG. 1 is a block diagram showing a prior art disk control system. This disk control system comprises a SCSI control circuit for an optical disk.
In this disk control system, an optical head 2 reads out data written on an optical disk 1 and also writes data on the optical disk 1. The optical disk 1 is rotated by an appropriate driving device. R(Read)/W(Write) amplifier 3 amplifies data signals detected by the optical head and outputs this amplified signals to a format control circuit 4 RIN amplifier 3 also amplifies the output signals from the format control circuit 4 and outputs the amplified signals to the optical head 2. The format control circuit 4 receives signals from the R/W amplifier 3 and detects the desired sector by reading the ID (address information for the sector) recorded on the top of each sector of data written on the surface of the optical disk 1. To a bus connecting this format circuit 4 and the SCSI control circuit 7 is connected a buffer memory 5 which temporarily stores various data. This buffer memory 5 is controlled by a buffer memory control circuit 6.
The SCSI control circuit 7 transmits and receives data to and from a host system and the like through the SCSI bus 13. A servo control circuit 8 controls the position of the optical head 2 relating to the optical disk 1. The servo control circuit 8 is controlled by a drive controller 10.
The SCSI control circuit 7, buffer memory control circuit 6 and format control circuit 4 are connected to a system controller bus 14. The system controller 11 comprising a microprocessor communicates with the host system through the SCSI bus 13 and the SCSI control circuit 7 and is connected to both the buffer memory control circuit 6 and the format control circuit 4 through the system controller bus 14 system controller 11 is also connected to the drive controller 10 through bus 15. The system controller 11 controls the center disk control system through the system controller bus 14 according to a command from the host system. Also, a main memory 12 is connected to the system controller bus 14 and stores various data input through this system controller bus 14.
The operation of the prior art disk control system constructed as aforementioned will be described. When a command for data write is input to the SCSI control circuit 7 through the SCSI bus 13, the write command is transferred to the system controller 11 through the system controller bus 14. Then, the system controller 11 commands the drive controller 10 to move to the track at the desired position to initiate the write operation in the optical disk 1 (hereinafter referred to as seek). Simultaneously, the system controller 11 sets up the addressing and the like in the buffer memory 5 for the buffer memory control circuit 6 and the data input-output mode with the host system for the SCSI control circuit 7. Data transferred from the host system is temporarily stored in the buffer memory 5 by the SCSI control circuit 7.
Once the format control circuit 4 detects the desired sector by reading the ID placed on the top of each sector in the optical disk 1 through the optical head 2 and the R/W amplifier 3, the system controller 11 reads data stored in the buffer memory 5 and conducts the addition and modulation of synchronization pattern. These data are written in the optical disk 1 through the R/W amplifier 3 and the optical head 2.
In the case of a command for a data read operation input to the SCSI control circuit 7 through the SCSI bus 13, this data read command transferred to the system controller 11 through the system controller bus 14. Then, the system controller 11 commands the drive controller 10 to seek the appropriate track to initiate the read operation from the optical disk 1. Simultaneously, the system controller 11 commands the buffer memory control circuit 6 to set the addressing of read and the like in the buffer memory 5 and awaits.
Once the format control circuit 4 detects the desired sector by reading the ID placed on the top of each sector from the optical disk 1 through the optical head 2 and the R/W amplifier 3, the system controller 11 reads data of that sector and writes it in the buffer memory 5. The SCSI control circuit 7 transfers all data stored in the buffer memory 5 to the host system through the SCSI bus 13.
In the prior art disk control system constructed as mentioned above, faulty articles can occur during manufacturing process as well as after shipped to the market. According to the recent trend of miniaturizing the magnetic disk system and the optical disk system, it is difficult to identify its faulty point or block if such fault occurred in its disk control system.
Therefore, at most the disk control systems recently developed have a built-in self diagnostic function. For example, in order to conduct the diagnosis of the built-in memories, such disk control system is constructed to confirm the normality of its functioning by allowing to execute the write and read commands. In addition, the diagnosis of the data transfer functions is confirmed by transferring data previously stored in a memory for the diagnosis of the data transfer functions from one to another memories (DMA operation) and reading transferred data. Furthermore, in order to conduct the diagnosis of the error correcting circuit, it is confirmed that generated code is normal by inputting a selected sector data and executing the code generation command for the sector data. Such disk control system has also the self-diagnostic functions to perform the diagnostic of error correction by generating incorrect data in relation to the sector data including generated code. These self-diagnosis functions are usually performed immediately after power on or according to a requirement from the host system.
In the prior art disk control system, these self-diagnostic functions enables the system to manufacturing for faults and to easily correct such faults during the manufacturing process and after being shipped to the market.
The prior art disk control systems aforementioned, however, have a defect that abnormalities in the SCSI control circuit 7, if any, can not be detected because they are not installed with the self-diagnostic function for the SCSI control circuit as communicating means with the host system.